Seat Control Electronic System and Method for a Motor-Driven Motor Vehicle Adjusting Device

ABSTRACT

The invention relates to a seat control electronic system for controlling a drive of a motor vehicle seat which is configured for detecting a characteristic variable of the drive during several short actuations of the drive) and to evaluate variables respectively associated with several short actuations, and to determine a blocking function according to the evaluations.

FIELD OF THE INVENTION

The invention relates to a seat control electronic system which isdesigned to control and regulate a motor-driven motor vehicle seatadjusting device and has a trapping prevention function. The inventionalso relates to a method for controlling a motor-driven motor vehicleadjusting device, in particular a seat adjusting means.

BACKGROUND OF THE INVENTION

A trapping prevention guard is advantageous in motor-driven seatadjusting devices in motor vehicles for safety reasons, in order to stopand possibly reverse the motorized drive when necessary, that is to sayif an object or body part is trapped. Characteristic variables of themotorized drive can be evaluated in order to determine whether trappinghas occurred. Such characteristic variables are, for example, the motorvoltage, the motor current or the rotation speed. The motor moment canbe determined from these characteristic variables, and an excess forcecan be determined from the motor moment in turn. The excess force isgiven by the difference between the total force exerted by the motor anda total adjusting force which is required, in particular, to overcomethe friction and to accelerate the adjusting device. However, it isdifficult to determine the adjusting force since, for example, thefriction can vary during the course of the adjustment process on accountof areas with severe running difficulties. In addition, aging effects orelse temperature influences can have a considerable influence on thefriction. Temporarily varying acceleration forces are also taken intoaccount when determining the excess force.

According to EP 1 310 030 B1, a large number of individual forces areadded up at a summation point in order to determine a resulting excessforce and an excess force or a trapping force is determined bycomparison with the force currently exerted by the motor.

SUMMARY OF THE INVENTION

The invention is based on the object of providing a seat controlelectronic system and a method for detecting a trapping instance duringa seat adjustment operation as reliably as possible.

Accordingly, a seat control electronic system with a trapping preventionfunction for a motor-driven seat adjusting device is provided. The seatcontrol electronic system is formed and designed to determine anadjusting movement of a drive from at least one detected characteristicvariable of the drive. Furthermore, the seat control electronic systemis designed to determine trapping of an object or body part during aplurality of brief adjustment operations of the drive in the sameadjustment direction. In this case, a plurality of brief adjustmentoperations of the drive is to be understood as two, three or even moreadjustment operations performed by the user attempting, for example, touse the plurality of brief actuation operations to actuate a specificadjustment position by means of this jogging operation. It may not bepossible to determine a trapping instance during one of these adjustmentoperations itself on account of the brief duration of the actuationoperation.

In order to be able to evaluate a larger number of measured values fordetermining a trapping instance, the seat control electronic system istherefore formed and designed to determine a trapping instance frommeasured values of the characteristic variable of a first adjustmentoperation and from measured values of the characteristic variable of atleast a second brief adjustment operation. In this case, the firstadjustment operation can likewise be performed briefly, for example forone second.

The object is also achieved by a seat control electronic system of amotor-driven motor vehicle seat adjusting device which is formed tomonitor for a trapping instance from at least one detectedcharacteristic variable of a drive. The seat control electronic systemis designed to determine a first total load exerted by the drive duringa first adjustment operation. The seat control electronic system is alsodesigned to determine a second total load exerted by the drive after anadjustment break in the event of a second adjustment operation in thesame direction. The adjustment break is temporally defined between twoadjustment operations, so that these two adjustment operations areseparated from one another by this adjustment break.

In this case, the seat control electronic system does not delete anevaluation of the determined first total load if an adjustment path ofthe second adjustment operation falls below a threshold. The thresholdtherefore serves as a criterion on the basis of which the seat controlelectronic system distinguishes between a plurality of brief adjustmentoperations and a “normal” adjustment operation. In this case, a “normal”adjustment operation permits a trapping instance to be determined duringthis adjustment operation. If the adjustment path is below thisthreshold, the evaluation of the determined first total load fordetermining a trapping instance continues to be used. If the adjustmentdistance is above this threshold, the evaluation of the determined firsttotal load for determining a trapping instance is rejected since enoughmeasurement signals are available for detecting a trapping instance, inparticular during the second adjustment operation.

If the evaluation for the first adjustment operation is not deleted, theseat control electronic system is designed to stop the drive or reversethe adjustment direction of the drive if a trapping instance is detectedas a function of an evaluation of the first total load and the secondtotal load.

In this case, the motor torque is determined from detectedcharacteristic or actuating variables of the motor, for example themotor current, the motor rotation speed etc., as the total load. As analternative or in addition to the motor torque, it is also possible todetermine a characteristic variable, which represents the total load,directly from the characteristic variables of this type withoutdetermining the actual torque, or preferably to use the detectedcharacteristic variable, in particular the rotation speed detected, forexample, by means of a Hall sensor, directly as a criterion for thetotal load. The detected characteristic variable is thereforesimultaneously a direct representation of the total load. When therotation speed is used as a characteristic variable, it is possible toconclude, specifically from a drop in the rotation speed, that the totalload has increased. When a rotation speed-controlled DC motor is used, acontrol or actuating signal can be used instead of the rotation speed.

In a first development, provision is made for the seat controlelectronic system to be designed to determine and to store a firstnominal load during the first adjustment operation from the first totalload. The seat control electronic system is designed to determinewhether trapping has occurred during the second adjustment operationfrom a comparison between the first nominal load and the second totalload which varies during the second adjustment operation.

According to a second development, the seat control electronic system isdesigned to determine and store a second nominal load firstly during astart phase of the second adjustment operation from the second totalload. However, this is done only if the adjustment path of the secondadjustment operation exceeds the threshold. In this case, the controldevice is designed to determine whether trapping has occurred during amonitoring phase from a comparison between the second nominal load andthe second total load which varies during the second adjustmentoperation.

In an advantageous embodiment, the seat control electronic system isdesigned to delete the evaluation after the threshold is exceeded. Theseat control electronic system replaces the determined first nominalload with the second nominal load for the further determination of atrapping instance. The start phase advantageously corresponds to atranslatory adjustment path of up to 50 mm or an inclination adjustmentof approximately 1° of the adjusting device.

Depending on the possible structural design of a motor vehicle seat, aplurality of brief adjustment operations in the direction of the trappedobject or body part first lead to a significant trapping force. The seatcontrol electronic system is therefore preferably designed to determinea third total load or a further total load after a further adjustmentbreak in the event of a third adjustment operation and any further briefadjustment operation in the same adjustment direction.

Furthermore, the seat control electronic system is advantageouslydesigned to not delete an evaluation of the determined first total loadif an adjustment path of the third adjustment operation or of thefurther adjustment operation falls below the threshold. Instead, theseat control electronic system stops the drive or reverses theadjustment direction of the drive if a trapping instance is detected bythe seat control electronic system as a function of an evaluation of thefirst total load and the third total load.

The seat control electronic system is preferably designed to employ afirst mathematical model in order to determine the total load, inparticular during the first adjustment operation, and to change over toa second mathematical model which takes into account the trappinginstance only if there is a significant deviation between the total loadand the nominal load or if there is a significant deviation between thedetected characteristic variable during the second or a furtheradjustment operation for the assessing as to whether trapping hasoccurred.

The object according to the invention is also achieved by a seat controlelectronic system of a seat adjusting device of a motor vehicle which isformed and designed to detect a characteristic variable of a drive ofthe seat adjusting device during a plurality of brief actuationoperations of the drive. In this case, the seat control electronicsystem is designed to evaluate the values of characteristic variablewhich are in each case associated with the plurality of brief actuationoperations. The seat control electronic system determines a trappinginstance as a function of these evaluations of a plurality of actuationoperations.

During regular operation, that is to say during a continuous,uninterrupted actuation operation, provision is made for the total loadexerted by the motorized drive to be determined at the beginning of eachadjustment operation during a start phase and stored as the nominal loadof the adjusting device. In this case, the nominal load is made up, inparticular, of the frictional load which is to be overcome and theacceleration work. The start phase is followed by a monitoring phaseduring which the process determines whether trapping has occurred from acomparison, in particular by calculating the difference between thedetermined nominal load and the current total load. When a trappinginstance is identified, a countermeasure, for example stopping orreversal of the motorized drive, is again initiated.

One particular feature of this is the determination of the nominal loadat the beginning of the adjustment process. By means of this, thecurrent adjusting force is determined and used as a comparison value forthe monitoring phase. In this case, trapping is not monitored for duringthe start phase during regular operation. It is assumed here that notrapping has occurred during the start phase. This is based on theconsideration that it can usually be presumed in the case of seatadjustment that a person sitting on the seat or behind the seatinitially has a sufficient degree of freedom of movement or that theelasticity of the seat cushion is high enough for the person to not gettrapped at the beginning of the adjustment process. The adjustment pathis therefore assumed to be free during the start phase during which thenominal load can be determined from the total load exerted by the drive.

A trapping instance can be specifically precluded within this specifiedregion for the adjustment path. At the same time, this region is largeenough to determine the nominal load sufficiently accurately. Themechanical coupling means there is a direct correlation between thenumber of revolutions of the motor and the translatory adjustment pathor the adjustment path in the event of inclination adjustment. Specifictime windows or adjustment path sections for the start phase cantherefore be determined as a function of the respective system by meansof the rotation speed of the DC motor which is generally used. In thiscase, a translatory adjustment path is to be understood, in particular,as adjustment of the surface of the seat in the longitudinal direction.Translatory and rotary movements of the adjusting mechanism can be usedto exert the adjusting movement.

A mathematical model which is formed in the manner of a control loop canbe used when the total load of the motor is determined by evaluatingmotor characteristic variables. An actuating variable, for example themotor voltage, which influences control of the motor is used as an inputvariable for the mathematical model, and the current total load is thendetermined from this input variable. According to an expedientdevelopment, provision is now made to change over from a first model toa second model, which differs from the first, when there is asignificant deviation between the total load and the nominal load orwhen there is a significant deviation between the detectedcharacteristic variable and the variable correlated to the load, inorder to be able to use this second model to assess whether trapping hasactually occurred.

A changeover is made to the second model particularly when there is apredefined deviation of the rotation speed from an average rotationspeed, for example when the rotation speed drops to approximately 0.7times the average rotation speed. As an alternative, the characteristicvariable used for the changeover when there is a significant deviationmay also be, for example, the motor current and its deviation from anaverage motor current. This development is initially based on theconsideration that a significant or characteristic deviation may be anindication of a trapping instance, but that this is not yet sufficientto reliably assess a trapping instance. Different scenarios which couldlead to an increase in the total load without trapping occurring arepossible particularly in the trapping prevention guard for a seatadjustment means. Furthermore, it can be assumed here that, inparticular, a more sensitive mathematical model is required to make thedecision as to whether trapping has occurred. In contrast, this alsomeans that a simple algorithm which uses only few resources is used forthe first model in the normal case.

In this case, provision is preferably made for the first model to takeinto account the friction which occurs in the adjusting device and forthe second model to additionally comprise a spring model which takesinto account the trapping instance. The use of the spring model is basedon the consideration that the trapped person is pressed into the seatcushion in the event of a possible trapping instance. This may be theseat cushion of a back seat toward which a front seat is moved. However,it may also be the seat cushion of the front seat when the front seat ismoved forward toward the steering wheel or the dashboard. The soft seatcushion exerts a counter-force, with the value of the counter-forcebeing comparable with a spring force. The use of a spring model of thistype therefore permits decisions as to whether trapping has occurred tobe derived particularly by determining characteristic spring constants.In order to permit smooth transition between the two mathematicalmodels, at least some of the variables obtained with the first model areused as input variables for the second model when a changeover is madeto the second model.

The significant and characteristic deviation between the total load andthe nominal load used is preferably a limit value for the differencebetween these two load values being exceeded. In the present case of thebrief adjustment operations, the total load is preferably evaluatedduring the second adjustment operation or during a further, followingadjustment operation with the nominal load of the first adjustmentoperation by the difference between the total load of the second orfurther adjustment operations and the nominal load of the firstadjustment operation being compared with the limit value.

As an alternative or in addition, the situation of a limit value beingexceeded is preferably also used for differentiation of this differencewith respect to time or location, for example. The rotation speed isagain preferably used as the direct characteristic variable for the loadin this case. The nominal load is represented by an, in particularaverage, rotation speed. A rotation speed limit value is thereforeprovided, and a significant deviation is assumed to be present when thislimit value is undershot.

Furthermore, the average value of the total load or of the detectedcharacteristic variable which represents the total load is preferablyused during the first adjustment operation to determine the nominalload. In order to prevent this value for the nominal load from beingcorrupted by start-up effects, the total load of the motorized drivewhich occurs during a start-up phase is preferably not taken intoaccount. This start-up phase defines, for example, the region until themotor reaches its desired rotation speed. This is usually the case asearly as after a few revolutions of the motor.

Since different adjusting forces can occur over the adjustment path, forexample due to running difficulties, one expedient development makesprovision for the nominal load to also be determined during themonitoring phase of regular operation without adjustment breaks and tobe stored as the current nominal load which is used for the comparisonwith the total load during regular operation for subsequent measurementsof the characteristic variable during the monitoring phase. The nominalload is therefore also determined during the monitoring phase, inparticular continuously, starting with the value for the nominal loadwhich is determined during the start phase. The nominal load istherefore also tracked during the monitoring phase. In this case,discrete time windows can be provided, during which the nominal load isdetermined. As an alternative to tracking the nominal load, it is alsopossible, in principle, to use the value for the nominal load, whichvalue is determined during the start phase, for the entire actuatingprocess as a constant comparison value.

As soon as a significant deviation in the nominal load is detected, theactual nominal load, which was determined last, of the adjustmentoperation is stored and the further profile of the total load during asecond or further adjustment operation, in particular the differencebetween the total load and the stored nominal load or the differencebetween the values of the detected characteristic variables representingthe total load and the nominal load, is then checked for the presence ofa trapping instance. The situation of the significant deviation beingexceeded alone is not an adequate criterion for determining the presenceof a trapping instance since other situations, for example a localrunning difficulty or running-up against a mechanical stop, may bepresent. Identification of the significant deviation is thereforefollowed by a further check and evaluation of the profile of the totalload.

A total torque is preferably determined as the total load and a nominaltorque is preferably determined for the start phase from thecharacteristic variables of the motorized drive, with, in particular, aresulting moment, in particular a trapping moment, or a correlatedvariable being derived by calculating the difference. Furthermore, thetrapping moment is expediently weighted with a weighting parameter,which takes into account the mechanics of the adjusting device, fordetermining the resulting clamping force. In this case, the weightingparameter takes into account, for example, the lever length, the levertransmission ratio or the position of the adjusting mechanism. Inaddition, information about the areas of risk, that is to say, forexample, the distances between the seats, which are also dependent onthe body size in particular, are incorporated in the weightingparameters. In this case, the values of the weighting parameters arepreferably determined and stored with the aid of measurements on aphysical model. As an alternative, the values can also be determined bycalculation.

A spring model is expediently used as a basis for determining whethertrapping has occurred, and in particular at least one spring constant isdetermined, on the basis of which a decision is made as to whethertrapping has occurred. In this case, the absolute magnitude and/or theprofile of the spring constants, that is to say their derivative, are/ispreferably used to make the decision. The profile of the springconstants is used to make a distinction between different operatingsituations, specifically, in particular, a load movement, run-up againsta stop, a panic reaction, a running difficulty and trapping. At leasttwo determined values are expediently used for the spring constant, inorder to ensure reliable association. To this end, at least three loadthreshold values are preferably defined, between which the springconstant is determined, in particular by interpolation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: a schematic and simplified illustration of a physical conceptualmodel of an adjusting device, in particular of a seat adjusting means.

FIG. 2: a schematic and simplified illustration of a control loop for afirst mathematical model for describing the individual processes in theadjusting device.

FIG. 3: a schematic and simplified illustration of a second control loopfor a second mathematical model for describing the individual processesin the adjusting device, taking into account a trapping instance.

FIG. 4: a schematic and simplified illustration of the profile of themotor torque or the motor force with respect to travel or time.

FIGS. 5 and 6: schematic and simplified illustrations of force or torqueprofiles for different movement classes which occur during theadjustment movement.

FIG. 7: a schematic and simplified illustration of a force/travel graphin which the individual movement classes are associated with differentregions,

FIG. 8: a schematic and simplified illustration of a rotation speed/timegraph in which brief actuation operations of the adjustment means takeplace one after the other.

FIG. 9: a schematic and simplified illustration of a flowchart for atrapping prevention guard which distinguishes between continuous andbrief actuation.

DETAILED DESCRIPTION OF THE INVENTION

The method for reliable detection of a trapping instance explained belowwith reference to the figures applies to a motor-driven seat adjustingmeans in the motor vehicle sector. A device of this type has anadjusting mechanism which comprises a seat support which can usually belongitudinally adjusted in guide rails which are slightly inclined withrespect to the horizontal. A backrest whose inclination can be adjustedis also attached to the seat support. In this case, the rotation pointof the backrest is arranged such that it is somewhat spaced apart fromthe guide rails. Furthermore, the adjusting device comprises arespective drive motor both for translatory adjustment in thelongitudinal direction of the seat support and for inclinationadjustment of the backrest. These motors are usually a DC motor or arotation speed-controlled DC motor.

When seats are automatically adjusted, there is a risk of a person beingtrapped in the seat to be adjusted or else between the seat to beadjusted and a back seat. A trapping instance of this kind leads to ahigh motor torque and therefore correlates to a higher force expended bythe motor. This total torque generated by the motor is also generallycalled the total load in the present case. Identification of a trappinginstance is problematical particularly in the case of seat adjustment ofthis type since the force to be additionally applied by the motor doesnot necessarily exhibit an abrupt increase in the event of trapping onaccount of the soft seat cushion.

The computational and mathematical treatment of an adjusting device ofthis kind with the aid of a control device is explained in greaterdetail below with reference to FIGS. 1 to 3. In this case, FIG. 1 showsa physical conceptual model of an adjusting device of this type.According to this physical model, the motor voltage u is applied to themotor 2 during operation and a motor current i flows. The electricalcircuit has a non-reactive resistor R and an inductor L. A back e.m.f.u_(ind) is induced during operation.

On account of the motor current i, the motor exerts a motor momentM_(Mot) and drives a shaft 4 at a rotation speed n. The adjustingmechanism of the adjusting device is coupled to the shaft 4, this beingrepresented by the moment of inertia J. In addition, a load moment M_(L)is exerted by the adjusting mechanism, this load moment counteractingthe motor moment M_(Mot). The load moment M_(L) is made up of aplurality of moment components, for example a moment of friction M_(R)which is exerted on account of the friction of the adjusting device andcan additionally be superimposed with a moment of running difficultyM_(S).

In the event of trapping, a trapping moment M_(E) is additionally addedto the load moment M_(L). This trapping moment M_(E) has to bedetermined in order to be able to reliably identify trapping prevention.The problem here is that the further components of the load moment M_(L)are variable. It is particularly difficult to identify a trappinginstance in the case of trapping prevention for a seat adjusting meanssince the trapping force increases only slowly on account of thecompliance of the seat cushion and a distinction can be made, forexample, from a local running difficulty only with great difficulty.

In the event of trapping, a spring model is assumed in order tophysically and mathematically describe in a simple model the realprocesses when a person is trapped between the seat and a further seator the dashboard. In the physical model shown in FIG. 1, this isexpressed by the trapping moment M_(E) which contributes to the loadmoment M_(L) being characterized as a spring moment of a spring 6 whichcounteracts the motor moment M_(Mot). This spring 6 is furthercharacterized by a spring stiffness which is represented by means of aspring constant.

Taking this physical model as a basis, the following equation 1 is givenfor the motor voltage u:

u=R·i+L di/dt+u _(ind)  Equation 1

This can be differentiated to give the equation 1′ for the variabledi/dt:

di/dt=1/L(u−R·i−K ₁ n)  Equation 1′

with the following relationship, according to which the induced voltageu_(ind) is proportional to the rotation speed n and the proportionalityfactor is K₁, having been taken into account here:

u_(ind)=K₁n

Furthermore, the motor moment M_(Mot) is proportional to the motorcurrent i multiplied by a proportionality constant K₂:

M_(Mot)=K₂i  Equation 3

For the right-hand side of the physical model according to FIG. 1, thefollowing equation, according to which the difference between the motormoment M_(Mot) and the load moment M_(L) is proportional to the changein rotation speed n, with the proportionality factor being the moment ofinertia J, can be established for the torques:

M _(Mot) −M _(L) =Jdn/dt  Equation 4

The moment of inertia J is actually made up of several components, inparticular the moment of inertia of the motor and that of the mechanicalparts of the seat. Since very large transmission ratios are generallyprovided for motorized seat adjusting means, the proportion of the totalmoment of inertia of the mechanical parts can be ignored and it issufficient to take into account the moment of inertia of the motor forthe calculation. The following equation, according to which the trappingmoment M_(E) is proportional to the spring force F_(F), with theproportionality factor K₃ being a weighting parameter which takes intoaccount the geometry of the adjusting mechanism, can be derived from thespring model for the trapping moment M_(E). In this case, the weightingparameter takes into account, for example, the lever length, the levertransmission ratio or the position of the adjusting mechanism.Information about the areas of risk, that is to say, for example, thedistances between the seats which, in particular, are also dependent onthe body size, are additionally incorporated in the weighting parameter.The spring force F_(F) is in turn proportional to the rotation angleφ-φ_(K) covered, with the proportionality factor being the springconstant c. In this case, φ_(K) is the rotation angle at the time pointat the beginning of the trapping instance, that is to say when contactis made for the first time between the seat to be adjusted and thetrapped person.

M _(E) =K ₃ F _(F) =K ₃ c(φ-φ_(K))

A mathematical model or a corresponding calculation algorithm, which canbe represented by the control loop illustrated in FIG. 2 if the springmodel which represents the trapping instance is still not taken intoaccount, can be derived from this physical model. This control loopsubstantially represents the relationships according to equations 1 to4. Accordingly, the motor voltage u, as actuating signal, creates aspecific rotation speed

n. A change in the motor current i leads to a change in the voltage dropacross the non-reactive resistor R. Equally, a change in the load momentM_(L) leads to a change in the rotation speed and therefore to a changein the induced back e.m.f. These two voltage components act on the motorvoltage u again, so that a control loop is formed overall.

By taking into account the supplementary spring model, a secondmathematical model can be derived, with the aid of which the actualsituation can be checked for the presence of a trapping instance. Thissecond model can be represented by a control loop according to FIG. 3.This control loop is extended compared to the control loop according toFIG. 2 by means of the spring model, as is represented by equation 5.

The rotation angle φ is given by integration of the rotation speed n.The trapping moment M_(E) is built up on account of the spring constantc. The load moment M_(L) determined last by means of the firstmathematical model according to FIG. 2 is, as a constant variable fromthe first model, adopted as an input variable M_(L)′ for the secondmodel according to FIG. 3. The input variable M_(L)′ corresponds to anominal moment M_(G) which characterizes the total friction of thesystem. All of the variables incorporated in this second model,specifically the inductor L, the resistor R, the constants K₁ to K₃ andthe moment of inertia J of the motor, are known or can be determined andthe rotation speed and therefore the rotation angle can be measured. Thesingle unknown factor is the spring constant c which can thus bedetermined with the aid of a suitable algorithm on the basis of thesecond mathematical model.

The variables L, R and K₁ and K₂ are motor-specific characteristicvariables which are known when using a specific type of motor or atleast can be determined by experiments. The moment of inertia J and theconstant K₃ are variables which characterize the adjusting mechanism orthe interaction of the motor with the adjusting mechanism, whichvariables can be and also are likewise determined, in particular, byexperiments on reference models. In this case, the constant K₃ isdetermined separately for each type of adjusting device. In this case,the values of the parameter K₃ are measured and stored or theoreticallydetermined, particularly with the aid of measurements on an actual modelof the adjusting device. It should be noted here that, in particular,the weighting parameter K₃ which represents the mechanism of the seatadjusting means is dependent on other variables, for example angle ofinclination of the backrest or current longitudinal position of theseat. Therefore, a table of values or a characteristic map for theparameter K₃ is created overall and stored in a memory of the controldevice. The respectively valid parameter values are then taken from thistable of values or characteristic map in each case depending on thecurrent position of the seat, and adopted in the calculation for thefirst or second model. In this case, the values of these parameters canalso be processed using fuzzy logic.

FIG. 4 illustrates a typical profile of the motor moment M_(Mot) withrespect to the adjustment path x or else with respect to time t. Theforce F exerted by the motor can also be plotted instead of the motormoment M_(Mot). It is not absolutely necessary to determine and toevaluate the motor moment. It is sufficient to determine or additionallyuse and evaluate a variable which correlates to the exerted force F. Thecorrelated variable is, for example, the detected rotation speed n.

In the method, a distinction is made between a start phase I and amonitoring phase II. The start phase I is divided into two sub-phasesI_(A) and I_(B), with the sub-phase I_(A) representing a start-up phaseof the motor 2 during which the motor 2 is adjusted to a specific,substantially constant motor moment M_(Mot). The motor moment M_(Mot)remains at this level if there are no frictional changes, runningdifficulties or trapping situations.

The second sub-phase I_(B) serves to determine a nominal moment M_(G).This corresponds to the motor moment M_(Mot) which is output by themotor 2 during this sub-phase I_(B) and is also called the total momentor total load. The nominal moment M_(G) is determined, in particular, bycalculating the average value of the values for the motor moment M_(Mot)over the second sub-phase. As an alternative to this, the average valueis calculated over the entire start phase I and the start-up effects areignored.

The start phase I becomes the monitoring phase II at a time point t₀. Inthis case, the time point t₀ is formed such that the adjusting devicehas covered a predefined adjustment path up until this time point. Thevalue for the nominal moment M_(G) determined during the start phase Iis first stored as a comparison value for the monitoring phase II.During the monitoring phase II, a significant or characteristicdeviation is defined as a difference from the nominal moment M_(G) and alimit value which is called lower load value M₁ is stored. The profileof the motor moment M_(Mot) is now monitored in order to determinewhether this lower load limit value M_(L) is exceeded. In this case, theaveraged profile of the rotation speed n is used as a criterion for theprofile of the motor moment M_(Mot).

In this case, both the value for the nominal moment M_(G) and, with it,the lower load value M₁ are preferably adapted during the adjustmentprocess. Different frictional values and local running difficultiesusually occur, specifically over the adjustment path, so that the motormoment M_(Mot) varies and, for example, also increases continuously overa relatively long adjustment path. If the nominal moment M_(G) were notadapted, there would be a risk of the load value M₁ being exceeded, thisbeing a triggering criterion for checking whether trapping has occurred.In this case, the nominal moment M_(G) is adapted, for example, bymoving average value calculation over a predefined time window or elseby means of continued average value calculation, starting from timepoint t₀.

If the load value M₁ is exceeded, this is judged to be an indication ofa possible trapping instance. At this time point, a changeover is madefrom the first mathematical model to the second mathematical model andthe spring model is now taken into consideration for the calculation.When the changeover is made to the second model, at least one variablewhich is still determined with the first model is adopted here as aninput variable for the second model. This variable is, for example, thevalue for the last actual nominal moment M_(G), since this representsthe sum of all the moments acting on the drive, excluding the trappingmoment M_(E).

The changeover to the second mathematical model is therefore made attime point t_(A), at which the load value M_(L) is exceeded. Therefore,the monitoring phase II is also divided into two sub-phases II_(A) andII_(B), with the first mathematical model being used for monitoringpurposes during the first sub-phase II_(A) and the second mathematicalmodel being used during the sub-phase II_(B).

The second mathematical model is now used to check whether trapping hasactually occurred. This is explained in greater detail below withreference to FIGS. 5 to 7. If it is established during this checkingoperation that trapping has occurred, the motor 2 is automaticallystopped and possibly reversed. If it is established that trapping hasnot occurred, a changeover is then made to the first mathematical modelagain and the sub-phase II_(A) of the monitoring phase II is continued.

When checking a seat adjusting means for a trapping instance, theprofile of the motor moment M_(Mot) is examined to determine which ofthe following movement classes are present:

-   -   a) running difficulty of the adjusting device,    -   b) trapping of an object, with a distinction being made here        between two trapping situations b1, b2,    -   c) run-up against an end stop,    -   d) sudden reaction (panic reaction) and    -   e) load movement.

The characteristic profiles for these movement classes of the motormoment M_(Mot) are illustrated in FIGS. 5 and 6. As can be seen from theindividual curve sections in FIGS. 5 and 6, the movement class a) forrunning difficulty is distinguished by a slow increase in moment. Hightorques are not usually reached in this case. In contrast to this, thecurve profile for the movement class for the trapping instance b) isdistinguished by a somewhat steeper increase. In this case, the trappingsituations can occur, in principle, of a virtually immovable objectbeing trapped. Taking the spring model, which represents the physicalreality very well, as a basis, this means a uniform, linear increase inthe force exerted by the motor 2 and therefore in its motor momentM_(Mot). This corresponds to the curve section according to b₁. However,it is usually expected that the person exerts a certain counter-force.This is illustrated by the curve profile according to b₂, according towhich the increase in moment is progressive and not linear.

The movement class c) is distinguished by a sharper increase in forcecompared to movement class b), since here the seat mechanism movesagainst a mechanical stop. The increase is usually linear in this casesince the mechanical stop is characterized by at least a constant springrate or spring constant c and the force therefore builds up linearlyproportionally to the distance covered. In contrast to this, in the caseof a load movement (movement class e)), that is to say, for example,movement of the person on the seat during the seat adjustment process,an increase in force which is similar to the amount of movement can beidentified, but with the profile of the increase in force no longerbeing linear like in the event of run-up against the mechanical stop.

Finally, a further movement class d), specifically that of a panicreaction, is defined. It is assumed here that, in certain situations,the person responds to the risk of being trapped with a sudden reaction.This is generally expressed by the person bracing himself against theadjusting movement with all his force. This creates a very steepincrease in force. A strictly linear profile is not to be expected hereeither.

In the spring model which forms the basis, the increase in force ormotor moment M_(Mot) corresponds to the gradient or derivative, andtherefore to the spring constants c, for evaluation of these differentsituations. Therefore, the spring constant c, which can be obtained bymeans of the derivative, is used as the decision criterion as thecritical criterion for classifying the currently measured profile of themotor moment M_(Mot). In addition, further decision criteria, which haveto be satisfied, are provided for unambiguous association. The term“derivative” is to be understood very broadly here. It is essential forcharacteristic variables for the profile of the respective motor momentM_(Mot) to be determined, from which characteristic variablesconclusions can be drawn as to which movement classes a) to e) arepresent.

In the exemplary embodiment, an average load value M₂ and a maximum loadvalue M₃ are defined in addition to the lower load value M₁ in order toidentify the different movement classes. If the respective load value M₁to M₃ is reached, the associated adjustment path x₁ to x₃ (or else theassociated time point t) is stored and value pairs (M₁, x₁), (M₂, x₂)and (M₃, x₃) are respectively formed. As an alternative to this, it isalso possible to predefine fixed travel points during the sub-phaseII_(B) and to determine the respectively current motor moment M_(Mot) atthese travel points.

A value for the gradient c₁, c₂ is then determined in each case from thevalue pairs, in particular by simple linear interpolation or anothermathematical interpolation. This is indicated in FIG. 5 in relation tomovement class b2. The computational outlay is very low due to theevaluation of only three discrete value pairs. As an alternative tothis, it is of course possible to determine the derivative continuously.

Some movement classes a) to e) differ additionally or sometimes only byvirtue of the profile of the increase. By determining three value pairs,two intervals are used for evaluation purposes, so that it is possibleto identify whether the increase in force is increasing, remaining thesame or possibly even decreasing.

In addition to the decision criterion of the derivative (gradient c1,c2), a further decision criterion used is the maximum load value M3being exceeded. Therefore, a trapping instance is identified only whenthe derivative moves in a predetermined value range and at the same timethe maximum load value M₃ is exceeded. With regard to the derivative,the decision value used is not only the absolute value but also theprofile of the absolute value.

As can be seen from comparison of FIGS. 5 and 6, it is of criticalimportance for the movement class for the panic reaction d) to be takeninto account as such. The movement classes b1) and b2) representtrapping situations, but the movement classes c) and e), specificallyrun-up against an end stop and load movement, lie between these twotrapping situations. However, it is undesirable to switch off or reversethe motor, particularly in the case of load movement. Therefore, highdecision reliability for identifying a trapping instance, without havingto accept losses in comfort, is possible only by checking the curveprofile for such a panic reaction.

The derivative is of particular importance for associating the currentlymeasured profile with the individual movement classes a) to e). Forassociation in terms of which value of the derivative or which profileof the derivative is to be associated with which of the movement classesa) to e), it is expedient—similarly to in the case of the weightingfactor K₃—to store the individual values or profiles of the derivativein a table or in a characteristic map from which association with theindividual movement classes can be performed directly or with the aid ofa fuzzy logic, taking into account further boundary parameters. In thiscase, the table or the characteristic map is preferably likewisedetermined in the manner of a calibration process on the basis of aspecific physical model, or empirical values are employed.

FIG. 7 illustrates a force/travel graph which is derived from such acharacteristic map and in which the individual regions which are to beassociated with the movement classes a)-e) are separated from oneanother by dashed lines. Furthermore, a force profile with a progressiveincrease in force in the event of trapping is plotted, by way ofexample, with the determined gradient values c1, c2.

FIG. 8 shows a graph in which a rotation speed n of the motor 2 isplotted against time t, by way of example. Three adjustment operations1V, 2V and 3V, which are separated from one another by two adjustmentbreaks Δt_(p12) and Δt_(p23), are illustrated. During the firstadjustment operation 1V, the rotation speed n reaches the first valuen_(1V). A first motor moment M_(Mot1) is determined as the first totalload from the rotation speed n during this first adjustment operation1V. During the second adjustment operation 2V, the rotation speed nreaches the second value n_(2V) which is lower than the first valuen_(1V). A second motor moment M_(Mot2) is determined as the second totalload from the rotation speed n during this second adjustment operation2V. During the third adjustment operation 3V, the rotation speed nreaches the value n_(3V) which is in turn lower than the second valuen_(2V). A third motor moment M_(Mot3) is determined as the third totalload from the rotation speed n during this third adjustment operation3V. This reduction in rotation speed n over the three adjustmentoperations 1V, 2V and 3V is intended to schematically illustrate atrapping instance which can occur in the event of a plurality of briefactuation operations of an adjusting device in the same adjustmentdirection and can be determined by a seat controller, as explainedbelow.

The adjustment operation 1V is started at time point t_(on1). In thiscase, the region bounded by dashed lines corresponds to the sub-phaseI_(A) which represents the start-up phase of the motor 2. In thisstart-up phase of the motor 2, the motor 2 is accelerated to therotation speed n_(V1). The rotation speed n can be varied during thefirst adjustment operation 1V, this not being illustrated in FIG. 8 inorder to simplify the illustration. The motor moment M_(Mot1) and thenominal moment M_(G) are determined from the rotation speed n during thefirst adjustment operation 1V. The first adjustment operation 1V isterminated at time point T_(off1), and the value for the nominal momentM_(G) is kept stored.

The second adjustment operation 2V is started at time point t_(on2). Therotation speed n reaches the value n_(2V) after the start-up phase ofthe motor 2. The current second motor moment M_(Mot2) is determined fromthis value. Since a shorter adjustment path Δx(2V) than a threshold(Th_(x), see FIG. 9) is covered during the second adjustment operation2V, the value for the nominal moment M_(G) stored up until this pointcontinues to be stored and is used as an input variable for the trappingprevention algorithm. In order to detect a trapping instance, the motormoment M_(Mot2) during the second adjustment operation 2V is evaluatedtogether with the nominal moment M_(G) for determining a trappinginstance. The second, brief adjustment operation 2V is terminated attime point t_(off2).

The third adjustment operation V3 is started at time point t_(on3). Thisthird adjustment operation likewise lasts only briefly, so that ashorter adjustment path Δx(3V) than a threshold (Th_(x), see FIG. 9)which correlates with an adjustment distance is covered during the thirdadjustment operation 3V. The nominal moment M_(G) determined during thefirst adjustment operation 1V continues to be stored and is used as aninput variable to determine a trapping instance. The current third motormoment M_(Mot3) which is determined from the speed n_(3V) is evaluatedtogether with the stored nominal moment M_(G) during the thirdadjustment operation 3V.

A portion of the algorithm is schematically illustrated as a flowchartin FIG. 9. The algorithm is started in step 1. The start can beinitiated in an adjustment direction, for example, by a first actuationoperation. A nominal moment M_(G) is then continuously determined duringthe adjustment operation in step 2. If the adjustment path Δx coveredreaches a threshold Th_(x) in step 3, a trapping instance is determinedwith the determined nominal moment M_(G) in step 4. If a trappinginstance can be determined, the adjustment operation is stopped orreversed in step 6. Otherwise, the nominal moment continues to becontinuously determined in step 2.

If the adjustment path Δx covered in step 3 is smaller than thethreshold Th_(x), a trapping instance is determined in step 5. In thiscase, the input variable used for this determination is the nominalmoment M_(G) which was determined in a preceding adjustment operationand is still stored. If a trapping instance cannot be determined in step5, the threshold value comparison is then performed again in step 3. Ifthe adjustment path Δx covered is greater than the threshold Th_(x) instep 3, the nominal moment M_(G) is determined again in step 2, possiblyfollowing step 4. Otherwise, the adjustment operation is stopped in step6, following identification of a trapping instance in step 5.

1. A seat control electronic system having a trapping preventionfunction for a motor-driven seat adjusting device, with the seat controlelectronic system being configured to determine an adjusting movement ofa drive from at least one detected characteristic variable of the drive,and to determine a trapping instance from measured values of thecharacteristic variable of a first adjustment operation and frommeasured values of the characteristic variable of a second and/orfurther brief adjustment operations during a plurality of briefadjustment operations of the drive in the same adjustment direction. 2.The seat control electronic system according to claim 1, wherein saidseat control electronic system is configured to determine a first totalload exerted by the drive during the first adjustment operation, todetermine a second total load exerted by the drive after an adjustmentbreak for the second adjustment operation in the same adjustmentdirection, to not reject an evaluation of the determined first totalload if an adjustment path or adjustment time of the second adjustmentoperation falls below a threshold, and to stop the drive or to reversethe adjustment direction of the drive if a trapping instance is detectedas a function of an evaluation of the first total load and the secondtotal load.
 3. The seat control electronic system according to claim 2,wherein said seat control electronic system is configured to determineand to store a first nominal load during the first adjustment operationfrom the first total load, and which is configured to determine whethertrapping has occurred during the second adjustment operation from acomparison between the first nominal load and the second total loadwhich varies during the second adjustment operation.
 4. The seat controlelectronic system according to claim 2, wherein said seat controlelectronic system is configured to determine and store a second nominalload first during a start phase of the second adjustment operation fromthe second nominal load if the adjustment path of the second adjustmentoperation exceeds the threshold, and to determine whether trapping hasoccurred during a monitoring phase from a comparison between the secondnominal load and the second total load which varies during the secondadjustment operation.
 5. The seat control electronic system according toclaim 4, wherein, in order to delete the evaluation after the thresholdis exceeded, the seat control electronic system is configured to replacethe determined first nominal load with the second nominal load for thefurther determination of a trapping instance.
 6. The seat controlelectronic system according to claim 4, in which the start phasecorresponds to a translatory adjustment path of up to 50 mm or aninclination adjustment of approximately 1° of the adjusting device. 7.The seat control electronic system according to claim 2, which isdesigned to determine a third total load after a further adjustmentbreak in the event of a third adjustment operation in the sameadjustment direction, to not delete an evaluation of the determinedfirst total load if an adjustment path of the third adjustment operationfalls below the threshold, and to stop the drive or to reverse theadjustment direction of the drive if a trapping instance is detected asa function of an evaluation of the first total load and the third totalload.
 8. The seat control electronic system according to claim 1,wherein the seat control electronic system is configured to employ afirst mathematical model in order to determine the total load, and tochange over to a second mathematical model which takes into account thetrapping instance only if there is a significant deviation between thetotal load and the nominal load or if there is a significant deviationbetween the detected characteristic variable for assessing whethertrapping has occurred.
 9. The seat control electronic system forcontrolling a drive of a motor vehicle seat, which is configured todetect a characteristic variable of the drive during a plurality ofbrief actuation operations of the drive, to evaluate the characteristicvariable which is in each case associated with the plurality of briefactuation operations, and to determine a trapping instance as a functionof these evaluations of a plurality of actuation operations.
 10. Amethod for controlling a motor-driven motor vehicle adjusting device,wherein a total load that is exerted by the drive is derived from atleast one detected characteristic variable of a drive in order tomonitor for a trapping instance, with a first total load beingdetermined during a first adjustment operation, a second total loadbeing determined after an adjustment break in the event of a secondadjustment operation in the same adjustment direction, an evaluation ofthe determined first total load not being rejected if an adjustment pathor adjustment time of the second adjustment operation falls below athreshold, and the drive being stopped or the adjustment direction ofthe drive being reversed if a trapping instance is detected as afunction of an evaluation of the first total load and the second totalload.
 11. The method according to claim 10, in which a first nominalload is determined and stored during the first adjustment operation fromthe first total load, and in which the process determines whethertrapping has occurred during the second adjustment operation from acomparison between the first nominal load and the second total loadwhich varies during the second adjustment operation.
 12. The methodaccording to claim 10, in which a second nominal load is determined andstored first during a start phase of the second adjustment operationfrom the second total load if the adjustment path of the secondadjustment operation exceeds the threshold, and in which the processdetermines whether trapping has occurred during a monitoring phase froma comparison between the second nominal load and the second total loadwhich varies during the second adjustment operation.
 13. The methodaccording to claim 11, in which, in order to delete the evaluation afterthe threshold is exceeded, the determined first nominal position isreplaced with the second nominal load for the further determination of atrapping instance.
 14. The method according to claim 10, wherein a thirdtotal load is determined after a further adjustment break in the eventof a third adjustment operation in the same adjustment direction, anevaluation of the determined first total load and/or an evaluation ofthe determined second total load is not deleted if an adjustment path ofthe third adjustment operation falls below the threshold, and the driveis stopped or the adjustment direction of the drive is reversed if atrapping instance is detected as a function of an evaluation of thefirst total load and the third total load.